Practical, economical and elegant structural designs

How green can you get?

The BREEAM level to be achieved for a new home should be agreed with the client early on. Level 4 is usually a planning requirement these days.

Making the jump to level 5 or 6 need not be unduly costly, provided you appoint a design team that has achieved level 5 before, a Code and SAP assessor who provides continuous feedback on how the design team decisions are affecting the scoring and a contractor with the right degree of experience whose diligence will allow the successful outcome. The jump between level 5 and level 6 can be summarise by the consideration of the unregulated energy use which includes cooking, electrical appliances such as televisions and computers.

There are plenty of factors to be considered at the outset. A fundamental one is the orientation of the building to maximise solar gain and level of energy production with solar panels. Others include the approach that’s to be taken to water harvesting and usage; the degree of airtightness that is to be achieved; the insulation standard to be met; the thermal modelling of each junctions reducing thermal bridging; the building materials to be employed; and the uses to which the building is to be put.

We have just finished a code 6 homes at Severn Rd – the only one in? and this is how the home scored under each categories (out of 100 points allocated):

Energy 90

Water 100

Materials 75

Surface water-run off 50

Waste 87

Pollution 100

Health and Wellbeing 100

Management 100

Ecology 77

The total cost of the substructure and superstructure on Severn Rd was £195,000 following the breakdown below:

Enhanced timber frame £35,000

Beam and polysterene infill block floor £12,000

Tripe glazed windows and doors £11,000

Additional air barriers and tapes £2,000

M+E services and renewable technologies £57,500

Additional fees £3,900

The total cost of the project was £365,000.

We have estimated that to achieve Code 6 zero carbon from code 4, on Severn Rd, the extra cost was of £50,350 and are distributed as below:

Timber frame + insulation: + £10,000

Beam and Block floor: + £2,750

Roof insulation: + £1,500

Windows: + £3,500

Air permeability: + £2,600

M+E: + £30,000

However looking at the average energy bills in the UK which is £1,420 per year compared to expected bills of £307 per year on Severn Rd. A saving of £1,113 per year!

If you get the right people on board, achieving BREEAM level 6 need not be the scary and expensive business it’s often thought to be. It is shown from looking at the figures above, that the onset cost of doing level 6 will be offset throughout the life span of the house very easily.